Field of the Invention
The present invention relates to a light transmission device and more particularly to a light transmission device in which a plug provided at an end of an optical fiber is connected to a light transfer device including an electrical-optical ( E-O ) converter element, such as a light emission element, a light reception element, or the like, so as to transfer light between the optical fiber and the E-O converter element.
As such a light transmission device of this type, there has been proposed a device in which a receptacle of a light transfer device is formed by molding a synthtic resin material, the receptacle being integrally provided with an outward projecting plug-insertion cylindrical portion, the plug insertion cylindrical portion being formed with a plurality of slots each opened at the end surface of the plug portion to thereby divide the plug portion into a plurality of flexible engagement portions, each of the flexible engagement portions being provided with an engagement protrusion projecting from the inner surface of the tip end thereof, the receptacle being formed with a plug insertion hole opened at the plug insertion cylindrical portion, an E-O converter element such as a light emission element, a light reception element, or the like, is faced to the plug insertion hole, a clindrical plug being fitted to an optical piber at its end outer periphery, a flange projecting from the outer periphery of the plug and serving as an engament protrusion, the plug being inserted into the plug insertion hole from the plug insertion cylindrical portion.
In the thus arranged light transmision device, if the plug is inserted into the plug insertion hole through the plug insertion cylindrical portion, the flexible engagement portions are outward bent, get over the flange, and engaged by the flange. At this time, the respective end surfaces of the plug and the optical fiber are made into contact with the E-O converter element. Thus, through this connection, light transfer is achieved between the optical fiber and the E-O converter element.
Since an optical fiber core of the optical fiber was formed by a soft material such as acryl resin, however, the end surface of the optical fiber could be injured when it was brought into contact with the end surface of the E-O converter element and in that case the light transer could be be adversely affected.
Further, in a mold receptacle, the plug insertion hole could not be formed with precision of 1/100 mm order, while it could be formed with precision of 1/10 mm order. Furthermore, the length of the flexible engagement portions also could not be formed with high precision. For this, when the plug was inserted into the plug insertin hole, a gap might be formed between the end surface of the optival fiber and the end surface of the E-O converter element, the gap being not constant, resulting in risk of adverse effect on light transfer.